1. Field of the Invention
This invention relates generally to lawn mowers and, more particularly to rotary lawn mowers having one or more cutting blades mounted for rotation during operation about a generally vertical axis.
2. Description of Related Art
Generally speaking, there are two main categories of rotary lawn mower, namely: (1) a hover-type rotary lawn mower which, when operative, is supported by a cushion of air, and (2) a rotary mower which is supported on wheels and which may include a rear roller for producing a striped effect on a lawn during mowing.
Mowers falling under category (1) are manually propelled by a user whereas mowers falling under category (2) may be either manually propelled by a user or propelled by a drive-line taken from a power unit connectable via a clutch to one or more wheels or a roller system. In the latter case the power unit combines the functions of driving the rotatable cutting blade(s) and the mower per se.
Mowers falling within either category may be driven by either an internal combustion engine or an electric motor.
The height of cut of mown grass using a mower falling within both categories is varied by raising or lowering the position of the cutting blade relative to ground surface. In the case of category (1) mowers, it is common practice to change the vertical position of the blade on its drive shaft by adding or removing spacer washers encircling the drive shaft and disposed between the cutting blade and an abutment on the drive shaft. In the case of category (2) mowers, it is known for each wheel to be carried on an associated lever system which, upon angular displacement, raises/lowers the axis of rotation of a wheel and, consequently, the position of the cutting blade relative to the ground surface.
Rotary lawn mowers and rotary grass cutting machines have, since their inception, revolutionized lawn and grass maintenance in both and commercial fields. One great advantage of rotary mowers when compared with conventional cylinder mowers is that damp or even wet grass is cut more easily with the former than the latter. Further, utilization of the hover principle of mowers falling within category (1) renders them very maneuverable.
Early models of each category of rotary mower did not include a facility for grass collection and, consequently, cut or mulched grass cuttings were deposited on a lawn. Further, rotary lawn mowers which do not possess a grass-collecting facility usually leave a row of grass-cuttings, a so called windrow, on a lawn and alongside each line of cut thereby leaving an untidy appearance on a mown lawn. Assignee of the present invention was among the pioneers in overcoming this problem, or at least greatly reducing the same, by producing a rotary mower which positively collects mown grass and other debris from a lawn by suction and directs the same into a collector. Since, as indicated, the windrow is normally in the form of a row of grass cuttings alongside each line of cut, the area to which suction need be applied can be restricted to coincide with that part of a mower which overlaps that region where a windrow is expected to be formed. Alternatively, the region of suction collection can be divided into a number of sub-regions disposed at least across the trailing edge or behind the trailing edge of the mower or, if desired, around the total periphery of the mower.